Relays?

[The Veg]

So in my observation, a great many electrical questions here get answered with, 'put a relay on it.' Am I correct to surmise that everything in these cars should have a relay added to the circuit?

The question isn't entirely facetious. I'm having thoughts about refreshing/improving the electrics in my car at some point and am wondering the best way to approach it. Start over and design a new electrical system with more fuses and relays built-in from the start? Add improvements to the existing system?

[prezoom]

While attempting to straighten up the mishmash of wiring under the hood, I added some relays for three circuits. The air horns, new 14" puller radiator fan, and Miata/MX5 headlight motor. I used the original power circuits to power the relays, and ran new fused 44 strand/12ga wire to power the actual units. Probably should have done the same for the headlights. Will do that if I change the lights to something more powerful.

[mbell]

I am just starting work to design my own loom...

Already added relays etc but by time added stuff for other changes it all gets a bit messy so I'd rather do my own, with fuses relays and lots documentation.

If the car is staying very stock then it may make sense just to add a few relays to existing wiring but if few other changes may as well do it right.

[alan.barker]

While attempting to straighten up the mishmash of wiring under the hood, I added some relays for three circuits. The air horns, new 14" puller radiator fan, and Miata/MX5 headlight motor. I used the original power circuits to power the relays, and ran new fused 44 strand/12ga wire to power the actual units. Probably should have done the same for the headlights. Will do that if I change the lights to something more powerful.

I thought the Headlamps already have Relays
Alan

[billwill]

I thought the Headlamps already have Relays
Alan

They do but it seems that in the standard wiring the relays do not operate in a sensible way; their only action is to switch off the headlights when the pods are lowered. The full headlight current flows through the steering column switch and dashboard switch.

The circuit can be rearranged so that the switches handle only the coil current of the relays and the relay(s) switch the heavier bulb-current.


<typo corrected.. no change of meaning.>

[alan.barker]

Thanks Bill,
i've just learned something.
So it would be a good idea if i add 2 relays to my Sprint. 1 for main beam and 1 for dipped beam.
I could just unplug the bullets in each line near the Headlamps and insert the relays.
That way i don't need to change the wiring harness.
Alan

[Craven]

Alan,
Double check on the headlight relays on the later cars, it looks to me the high current feed comes directly from the ?B? terminal on the control box then switched by the relay.
Ron.

[Foxie]

Lotus wiring, like nearly all vehicles, is made from copper. Copper is expensive, and all manufacturers and especially a minimalist like Colin Chapman would use the lightest they could get away with. Light cable has more resistance, less overload safety margin, especially when dealing with high wattage bulbs, additional spotlights, overloaded motors etc.

Relays should be used where there is large current loads, i.e. headlamps, spotlamps, motors and horns. Motors and horns are also inductive loads, which arc at the switch when the circuit is broken, causing burning of switch contacts, and failure in the long term.

Relays mean the full power does not have to be routed to the dashboard switches, meaning shorter runs and less resistance losses, and facilitating the substitution of heavier cables to the individual loads. They avoid damage of rare Lotus dashboard switches and the hassle of replacing them. They minimize heat generation behind the insulating timber dashboard

The Plus 2 already had the main and dip headlamps, the horn, and the sidelights relayed. I have additionally relayed the kenlowe radiator fan, window winder motors, and low and high speed wipers. The improvement in window and wiper speeds was significant.

The 12 fuse system in the Plus 2 is a great improvement on the original 2 fuse system used in the Elan.

[gus]

Relays primarily allow smaller cheaper switches, or cuter integrated switches[think stalk mounted stuff]

The switches in these cars are not really a failure point.

Larger wire sizes for windows and better quality connections do a world of good.

Relays just add complexity and failure points.

I wired my windows with 14 ga wire to replace the something like 18 ga wire from Lucas. I also gave each of them their own fuse. One can now roll both windows up with the car off, something that would not happen before. Improving the wiring to the wiper motor also improved performance

[miked]

Bill,
I have never seen the steering column dip switch carrying lamp load current. On any Plus 2 or S4 that I have worked on the column stalk operates the relay coils as you would expect. The volt drop would be significant if as you describe. Not being argumentative. Check a drawing.

Mike

[The Veg]

The 12 fuse system in the Plus 2 is a great improvement on the original 2 fuse system used in the Elan.

Where are the other 10 located? I've only found 2 under the bonnet.

[billwill]

Thanks Bill,
i've just learned something.
So it would be a good idea if i add 2 relays to my Sprint. 1 for main beam and 1 for dipped beam.
I could just unplug the bullets in each line near the Headlamps and insert the relays.
That way i don't need to change the wiring harness.
Alan

The existing relays are OK, just needs the wiring reorganised.

[billwill]

Alan,
Double check on the headlight relays on the later cars, it looks to me the high current feed comes directly from the ?B? terminal on the control box then switched by the relay.
Ron.

It may well have been corrected on the later cars.

[gus]

I believe on the early 2 fuse cars, the headlight load is unfused

I would have to check a diagram, it has been a while

Also IIRC the micro switch on the dash headlight switch, switches all the ground current, which is why they are short lived. It is problematic to fix.

[elanner]

Don't forget these Hella fused relays as a very easy way to add fuses to the relay circuits. Available from Amazon, etc.

Nick

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